Northstar Engines and System Technical Discussion Discussion, 1993 Exploding Intake Plenum in Cadillac Engine Discussion; Several days ago when starting my Allante for the first time in the morning the intake plenum actually exploded, it ...

1993 Exploding Intake Plenum

Several days ago when starting my Allante for the first time in the morning the intake plenum actually exploded, it blew off the end near the power steering pump. I have since gotten a used one with injectors and all in tact. After reassembly it won't start- sounds as though it wants to start. The battery went dead after several days with the hood open. It was deduced that the fuel pressure sensor allowed the plenum to fill with excess gas and exploded after a mere nano second of cranking in the morning. Any ideas on what next - fuses were okay for the injectors. I just got these codes off it - P31 P52 P95 P109 No BCM Codes PCM?

THe only code that concerns me is P031 as to whether or not that would cause your problem, I will leave that to someone else.

I am not sure I agree with the conclusion that the fuel pressure regulator caused this, I believe you may have a leaky injector. I would be VERY careful with this problem, if this continues and fuel gets into a cylinder you COULD hydrolock the engine and put a rod through the side if it.

Re: 1993 Exploding Intake Plenum

by the way - one of the main reasons why cadillac didn't recall the plastic 93-94 fuel rails was because it was "inside the intake manifold" and deemed "safe" in the event of a fuel leak. Yeah, sure sounds like it.

Good thing nobody was standing under your hood when you started it up. Got any pictures? I would SERIOUSLY consider bringing in a lawyer to get cadillac to pay for your damages. Maybe a recall of these fuel rails would finally make all northstars safe.

Re: 1993 Exploding Intake Plenum

It could be just that wire that's faulty, or it could be due to trying to start it and then having the battery die, or ....

Looking at the coilpack, with the spark plug terminals being "up", remove the top connector on the right side (looking towards the firewall). Make sure there is no corrosion anywhere in it's 6 pins. I'd have to check the manual for any further instructions beyond that.

The MAP is under the intake top cover, near the throttle body, and may be either bolted down, or just held in with a grommet. I don't know in a 93. If it did explode, it may be just lying around in pieces... But you mentioned getting a new manifold, right? You should've got a new sensor as well. In that case, it may be just due to the old manifold's explosion.

Re: 1993 Exploding Intake Plenum

Yes - it is a Northstar. With an absolute piece of junk voltmeter I tried getting a reading off the coil packs while my daughter was cranking the engine- got nothing but when checking the remote battery post got 12v so I know I was grounded. So- I got no spark coming off any of the coil packs- thoughts anyone?

Re: 1993 Exploding Intake Plenum

Originally Posted by prosin

Yes - it is a Northstar. With an absolute piece of junk voltmeter I tried getting a reading off the coil packs while my daughter was cranking the engine- got nothing but when checking the remote battery post got 12v so I know I was grounded. So- I got no spark coming off any of the coil packs- thoughts anyone?

uhh.. reading off the tip of these?

(brass in this picture)? If so you may have killed your volt meter.

Look for the connector that looks like this:

but has 3 pins, and is on the driver's side of the coilpack. With the key in run, but the engine OFF, measure the voltage between the two outer pins. You should have 12 volts. If not, you've got a fuse/wire problem.

Re: 1993 Exploding Intake Plenum

I am not so sure it is not a fuel issue- I hear the pump running behind me- it shuts off and when I check the relief valve on fuel line there is no pressure or gas escaping. I think it would be impossible to get the two fuel lines that come up reversed- I also think those connectors are leaking a bit- how in the world do those get re-used successfully?